Reducing indigo coloring-matters.



UNETED tdith iftiilti i \VILHELIYI GAUS. OF LUD'VTIGSHAFEN-ON-THE-RHINE. GERIVKANY. ASE

NOR. "E0 BABI- SCHE ANILIN & SODA FABRIK. OF LUDV IGSHAE'EN-ON-EIil l-Ri'tlh ll ULHDJLANY. A

CGRPOBATION.

' REDUCING INDIGO t .ttti'i'fifli. Spes fication o No Drawing.

caustic alkali, and the spccil'lcation of Letters Patent No. 84-3566 describes" a modification ot the a'lmcsaid prom- 15 in whielra. part. or the whole. of tl alk: ii in replaced by an alkali salt of indigo white. or by an alkali carbonate. or alkali )linH ihate. or al' 'kalisrdtid. When either of thc atoresaid processes i;-: being carried out. it has been found in some cases that the acti n of the iron powder in' so tar unreliable that it will aometiines happen that the iron pmvder (say, powdered cast. iron tnrninga), even after having been freed from oily impurities, does; not always produce the beat in salts, althougl'i the iron powder hehavca normally if the reduction be carried out in the presence of acid. I have tound that the said unreliability can be. remedied and good results be alwaya obtained when reducing indigo, or similar coloring matter. with iron powder in-the preaence of alkali. or an alkaline. salt. as aforesaid it the iron pow der. before being; need for the reduction. be

treated Witn an acid.

This invention can be applied to iron powder generally and to iron residues, such as are obtained in chemical. processes and und-ar other conditions.

It possible that the. inability of the.

iron satisfactorily to reduce the indigo or similar coloring matter may be dne to a thin layer of ferric oxid covering the iron. and that the acid dissolves away this layer of ferric oxid. so that the n'ietallic. iron can then exert its reducing eti'cot upon the indigo. or similar coloring matter.

The following example will serve toillus- Application filed June 9,

COLORING-IVLFLET E1 53.

1 Letters ate atria ted 352:3 MM 2.

1910. Serial No. 565,987.

{tratc further-the natnrto'l" my invention and how it can he carried into practical ctfeet. but the invention W110i. contincd to this example; The part: are by weight. 'tv'tir three hundred part1-i ot very finely ground east-iron turnings (atter hating l'reed thcnn. it necensary. trom oil by treatiire them with carbon tetrachlorid) with one thousand parts of water, and then, while. well agi tating the mixture, add eighteen per cer. sulfuric acid. until a conaidcrable evolution of hydrogen commences. Then allow the. iron powder to settle. remove the acid liquor and wash the iron several times with water. The iron paste so obtained can be employed in the reduction ot indigo, or similar coloring matter in the manner described in the aforesaid spec-i iication.

N ow What; 1' claim is: i 1. he process of reducing indigo colon matters by means of iron which conts in first pickling the iron with an acid and then heating the indigo coloring matter in the presence of alkali with the iron which has been thus treated. substantially as hereinhet'm'e described. 1

2. 'iheproccsa of reducing indigo colorin matters by means of iron. which consirts the presence of cauetic alkali with the iron which hat. been thus treated. hllhH' intially as l'ier inheitore described.

it. The. process of reducing indiecolorinn matters by means: of iron which -on.-iists in first: pickling the iron with an a 'id and then heating the indigo color-inn matter in the. prcsei'ice of caustic alkali :olntion (\Yllit'll contains at least, 6.5 per cent..; of solid CtlttFitlt? alkali) with the iron which has been thin; treated. substantially as hereinbei'ore described.

in testimony whereof I have hcremito set my hand in the presence. of two subscribing witnesses.

. \VILHELM GAUS. \Viti'iesses J. Anni; Lnorn. ERNEST L. lives then heating: the indigo coloring matter in 

